The solution is to root the phone and then get to the corupt files and remove them. the phone will recreate the files and then the wifi will work. the unable to scan issue will be gone.
I have posted an article on my site with complete how to instructions.
here is the URL:
Samsung Galaxy S WiFi Issue Fix | BK Integration does IT easy
here are the steps.
1. First root the phone:to do this download the "GTS" (Galaxy S Tweaker) app from the android market place. Open the app and then run step one to install the the root access. the phone will restart.
2. After the restart download the android terminal app the name of the app is "Terminal Emulator"
3. Open the terminal app and then enter these commands.
- su (you will be prompted to give root access)
- cd /
- cd data
- cd wifi
- ls (you should see a file named "bcm_supp.conf"
- mv bcm_supp.conf bcm_supp.conf.bak
4. press the home key
5. power off the phone
6. power on the phone
7. enjoy your wifi again...
I hope that this helps, check out my site for further information.